The invention generally relates to communication, network elements, methods, apparatuses, systems and programs of or for routing of session requests or calls of a specific type such as emergency calls.
At least one or more embodiments of the invention relate to call support, e.g. emergency call support, in an internet protocol based system such as e.g. a multimedia subsystem. As an example, embodiments may be applied to an internet protocol multimedia subsystem, IMS, according to release 7, R7 IMS, or to any other type of system or release number. An example of IMS R7 emergency call support is described in standard.
As an example, when assuming that a user is always using a proxy call state control function, P-CSCF, in a visited network, a normal session control, e.g. an IMS session control, of a serving entity such as a serving call state control function may not be utilised. An emergency call state control function, E-CSCF, of a visited network may be provided for handling and routing emergency calls.
Yet not all access networks may have such an E-CSCF functionality available. Further, a terminal such as a mobile phone, personal digital assistant etc, may not be capable of handling an emergency call differently from any other call.